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  <title>Document</title>
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    body{
        text-align: center;
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  <style>
      div:last-child {
          display: none !important;
          opacity: 0 !important;
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      div:last-child div {
          display: none !important;
          opacity: 0 !important;
      }
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<body>
<H2>测试</H2>
<h3>可防止被删除</h3>
<div>红红火火恍恍惚惚或</div>
<div id="inject">inject inject inject inject inject inject </div>
</body>
</html>
